Many interventional medical procedures require that a medical device be inserted into the vasculature of a patient to perform a surgical operation on the patient. Often, it is necessary that such devices be reconfigured once they have been positioned in the vasculature. For instance, many medical procedures require the use of a device that can be inflated or expanded. Typically, in these cases, the device is attached to the distal end of a catheter, which is advanced through the vasculature to position the device at a lesion in a vessel of the patient. The device is then expanded or inflated at the lesion during the surgical operation. For example, the device could be a balloon or some other such device that is inflated to dilate a lesion in a vessel of the patient.
One common interventional medical procedure, which uses a balloon catheter, is percutaneous transluminal coronary angioplasty (PTCA). In a typical PTCA procedure, a dilatation balloon of the balloon catheter is advanced through the vasculature of a patient with the balloon in a deflated configuration. The balloon is then precisely positioned next to a lesion in the vessel that is to be treated. Once the balloon has been properly positioned, fluid is infused into the balloon to expand the balloon into an inflated configuration. As the balloon expands, it presses against the lesion and dilates the lesion to increase the effective diameter of the vessel. In turn, the portion of the lesion that is in contact with the balloon produces reactive forces on the balloon. For a lesion that is lubricious, the reactive forces may overcome the frictional forces between the balloon and the lesion. If this happens, slippage occurs between the balloon and the lesion, and results in unwanted movement of the balloon relative to the lesion. For instance, the reactive forces can cause the balloon to shoot forward or backward through the vessel in a longitudinal direction (i.e., “the watermelon seed effect”). This unwanted movement is to be avoided because the dilatation procedure does not occur precisely at the desired location in the vessel and, thus, the effectiveness of the PTCA procedure is reduced.
Various devices and methods have been suggested for preventing the unwanted longitudinal movement of a medical device as it is being expanded or inflated in the vasculature of a patient. For example, U.S. Pat. No. 5,620,418, which issued to O'Neill et al. for an invention entitled “Retrograde Coronary Sinus Catheter,” incorporates segmented, annular ribs on a balloon device for frictionally engaging the coronary sinus of the heart. The device disclosed in the O'Neill et al. reference, however, relies on a frictional component between the ribs and the coronary sinus to prevent unwanted movement of the device without penetrating the ribs into the walls of the coronary sinus. Other suggested devices for preventing unwanted movement of a medical device as it is being expanded or inflated in the vasculature incorporate structures for penetrating a lesion in a vessel of the patient. Typically, these structures are mounted on the outer surface of an inflatable balloon to penetrate the lesion as the balloon is being inflated. For example, U.S. patent application Ser. No. 09/927,135, which was filed by Jenusaitis et al. for an invention entitled “Balloon Anchoring System” and which is assigned to the same assignee as the present invention, incorporates stainless steel cutting blades with azimuthal segments that are mounted on the surface of a balloon. As the balloon expands in a vessel, the cutting blades and the azimuthal segments penetrate a lesion in the vessel to anchor the balloon to the lesion and thereby prevent unwanted movement of the balloon in the vessel. For these types of devices, however, the cutting blades and the balloon are separate structures that are typically made from different materials and that must somehow be joined together during manufacture. Typically, this manufacturing process is labor intensive and costly.
In light of the above, it is an object of the present invention to provide a system and method for preventing unwanted movement of a medical device while the device is being expanded or inflated in a vessel of a patient. Another object of the present invention is to provide a balloon with protuberances on the outer surface thereof for penetrating a lesion in a vessel of a patient, wherein the balloon and the protuberances are made of the same material. Still another object of the present invention is to provide a balloon that has protuberances seamlessly and integrally interconnected with the outer surface of the balloon for penetrating the protuberances into a lesion in a vessel of a patient to anchor the balloon to the lesion. Yet another object of the present invention is to provide a system for anchoring a medical device to a lesion in the vasculature of a patient that is relatively simple to manufacture, easy to use, and comparatively cost effective.